JP2015071662A - Thermally conductive silicone composition and cured product of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive silicone composition which provides a cured product having a coefficient of thermal conductivity of 1.5 W/m K or more and excellent moisture resistance without wearing a reaction vessel.SOLUTION: The thermally conductive silicone composition contains: (A) an organopolysiloxane having at least two alkenyl groups in one molecule; (B) an organohydrogenpolysiloxane having at least two SiH groups; (C) thermally conductive filler, 50 mass% or more of the total mass of which is occupied by magnesium oxide treated beforehand with a hydrophobic treatment agent (E); and (D) a platinum metal-based curing catalyst. The hydrophobically treated magnesium oxide is composed of (C-1) hydrophobically treated magnesium oxide powder having an average particle size of 0.1 to 40 μm and (C-2) hydrophobically treated magnesium oxide powder having an average particle size of 40 to 80 μm. A content ratio of components (C-1) and (C-2) is (C-1)/(C-2)=(1 to 3)/(2 to 4) by mass. The composition further contains aluminum oxide as thermally conductive filler.

Description

  In order to cool an electronic component by heat conduction, the present invention provides an interface between a heat boundary surface of a heat-generating electronic component and a heat dissipation member such as a heat sink or a circuit board, for example, between a heat-generating component and a heat-dissipating component in an electronic device. The present invention relates to a thermally conductive silicone composition that provides a thermally conductive silicone cured product that is installed and used for heat dissipation, and a cured product thereof.

  LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video disks, and mobile phones are becoming more and more themselves as performance, speed, size, and integration increase. Heat is generated, and the temperature rise of the chip due to the heat causes malfunction and destruction of the chip. Therefore, many heat dissipating methods for suppressing the temperature rise of the chip during operation and heat dissipating members used therefor have been proposed.

  Conventionally, in an electronic device or the like, a heat sink using a metal plate having a high thermal conductivity such as aluminum or copper is used in order to suppress a temperature rise of a chip during operation. The heat sink conducts heat generated by the chip and releases the heat from the surface due to a temperature difference from the outside air.

  In order to efficiently transfer the heat generated from the chip to the heat sink, it is necessary to closely attach the heat sink to the chip. However, because there is a difference in the height of each chip and tolerance due to assembly processing, a flexible sheet or grease is used. The heat transfer from the chip to the heat sink is realized through this sheet or grease.

  Grease-like heat dissipation material achieves low thermal resistance by thinning, but it is difficult to manage. In addition, in the application process, there are a case where the screen printing or the extrusion from the syringe is performed manually and a case where it is automatically performed using a dispensing device, but it takes a lot of time and is not easy to handle. There are cases where the product assembly process is rate limiting.

  A heat conductive sheet formed of a heat conductive silicone rubber or the like is excellent in handleability compared with grease and is used in various fields.

  In particular, the low-hardness heat conductive sheet can follow the unevenness between elements such as CPUs because of its shape flexibility, and does not hinder the downsizing of devices such as portable notebook personal computers. , Has the advantage of enabling efficient heat dissipation.

  Examples of the heat conductive filler in these heat conductive silicone cured products include alumina and aluminum hydroxide. In the case of a thermally conductive silicone cured product having a thermal conductivity in the range of 0.5 to 4 W / m · K, alumina is often mainly used as a thermally conductive filler from the viewpoint of cost and thermal conductivity. However, alumina has a very high Mohs hardness of 9, and wear of the inner wall of the reaction kettle and stirring blades is likely to proceed when a share is applied during the production of the heat conductive silicone composition. In addition, there is a concern that when the specific gravity is highly filled with 3.98 heavy alumina, the thermally conductive filler is likely to settle in the thermally conductive silicone composition. If sedimentation occurs, the composition will have a different moldability and the product cannot be produced stably. Then, if stirring and mixing is performed again before using the heat conductive silicone composition, sedimentation can be eliminated, but it also takes cost and time.

  On the other hand, aluminum hydroxide is attractive because it has a specific gravity of 2.42 and is lighter and cheaper than alumina. However, since the thermal conductivity is smaller than that of alumina, high filling is required when obtaining a silicone resin composition of 1.5 W / mK or more, which reduces the reliability of the silicone resin. Moreover, since heat resistance is inferior to an alumina, it is not suitable for the operation to the heat conductive sheet used under the high temperature of 150 degreeC or more.

  Examples of thermally conductive fillers other than alumina and aluminum hydroxide include aluminum, copper, silver, boron nitride, and aluminum nitride. They have high thermal performance, but are disadvantageous from the viewpoint of cost when obtaining a cured silicone resin having a thermal conductivity in the range of 0.5 to 4.0 W / mK. Furthermore, when aluminum, copper, silver, or the like is used, the insulating properties of the thermally conductive silicone composition and the cured product are lowered.

  Here, the thermal conductivity of magnesium oxide is 42 to 60 W / mK, which is notable in terms of being higher than that of alumina of 26 to 36 W / mK. Further, since the Mohs hardness of magnesium oxide is 6 and the specific gravity is 3.65, which is lighter than that of alumina, the above problems are hardly caused. However, it has a drawback of high hygroscopicity, and in Japanese Patent Laid-Open No. 5-239358 (Patent Document 1), magnesium oxide obtained by firing specific magnesium hydroxide at 1,100 to 1,600 ° C. is blended. Although a thermally conductive silicone rubber composition is disclosed, cracking is likely to occur in the silicone rubber because of its high hygroscopicity and as a result of exhibiting strong alkalinity.

  Japanese Patent Application Laid-Open No. 7-292251 (Patent Document 2) discloses a heat conductive silicone resin composition excellent in moisture resistance obtained by treating the surface of magnesium oxide with silazane. However, since the particle size of magnesium oxide is as small as 1 μm, no improvement in thermal conductivity can be expected even if the filling amount is increased, and this method is effective when using powder with a larger particle size. Has not been verified.

  Japanese Patent Application Laid-Open No. 8-88488 (Patent Document 3) discloses a thermally conductive heat-dissipating sheet in which formability is improved by combining spherical magnesium oxide and granular alumina. Magnesium oxide is a thermally conductive filler. Only about 20% by mass is used with respect to the total weight, and problems such as increase in specific gravity due to containing a large amount of alumina and wear of the reaction kettle during kneading have not been solved.

  Here, it can be said that a system in which surface-treated magnesium oxide and alumina are used in combination is effective in solving the above problem. When magnesium oxide and alumina are used in combination, a silicone resin composition having a thermal conductivity of 1.5 W / m · K or more is obtained with a lower filling amount and superior heat resistance than when magnesium oxide and aluminum hydroxide are used in combination. It becomes possible to do.

Further, by subjecting the surface of magnesium oxide to a hydrophobic treatment, the moisture resistance is improved, and a thermally conductive silicone resin composition suitable for use under high humidity can be obtained.
Further, by using 50% by mass or more of magnesium oxide in the total mass of magnesium oxide and alumina, it is possible to suppress the reaction kettle from wearing, and furthermore, with the same filling amount than using only alumina as a heat conductive filler. If it exists, since the specific gravity becomes lighter when alumina and magnesium hydroxide are used in combination, it is possible to suppress sedimentation of the heat conductive filler in the heat conductive silicone composition.

  In recent years, the size and weight of devices have been reduced. In order to reduce the weight of the entire device, there is a demand for lighter weight while maintaining performance in units of grams or milligrams in terms of members. From the viewpoint of weight reduction, a thermally conductive silicone composition having a thermal conductivity of 1.5 W / m · K or more and containing at least 50% by mass of magnesium oxide among the thermally conductive fillers containing magnesium oxide and alumina. Is also advantageous.

JP-A-5-239358 Japanese Patent Laid-Open No. 7-292251 JP-A-8-88488

  The present invention has been made in view of the above circumstances, and by composing a thermally conductive filler by combining hydrophobically treated magnesium oxides having different particle sizes at a predetermined ratio, without wearing the reaction kettle during kneading, Thermally conductive silicone composition having a thermal conductivity of 1.5 W / m · K or more and excellent in moisture resistance under high temperature and high humidity (thermally conductive heat dissipation sheet) and cured product thereof The purpose is to provide.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have determined that the surface of the surface is previously hydrophobized as magnesium oxide having an average particle size of 0.1 μm or more and less than 40 μm, and an average particle size of 40 μm. By combining magnesium oxide of less than 80 μm in a predetermined ratio and using magnesium oxide hydrophobized in this way in an amount of 50% by mass or more based on the total mass of the thermally conductive filler, the thermal conductivity is 1.5 W. The present inventors have found that a thermally conductive silicone composition that gives a thermally conductive silicone cured product with moisture resistance at / m · K or more and a cured product thereof can be obtained, and have made the present invention.

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００の整数である。）
で表される分子鎖片末端がトリアルコキシシリル基で封鎖されたジメチルポリシロキサン
であることを特徴とする〔１〕記載の熱伝導性シリコーン組成物。
〔３〕
（Ｃ）熱伝導性充填材として、さらに酸化アルミニウムを含む〔１〕又は〔２〕記載の熱伝導性シリコーン組成物。
〔４〕
さらに、（Ｆ）成分として、下記一般式（１）のアルコキシシラン化合物及び／又は一般式（２）のジメチルポリシロキサンを（Ａ）成分１００質量部に対して０．０１〜５０質量部添加してなる〔１〕〜〔３〕のいずれか１項記載の熱伝導性シリコーン組成物。
Ｒ¹ _aＲ² _bＳｉ（ＯＲ³）_4-a-b （１）
（式中、Ｒ¹は独立に炭素原子数６〜１５のアルキル基であり、Ｒ²は独立に非置換又は置換の炭素原子数１〜１２の１価炭化水素基であり、Ｒ³は独立に炭素原子数１〜６のアルキル基であり、ａは１〜３の整数、ｂは０〜２の整数であり、但しａ＋ｂは１〜３の整数である。）

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００の整数である。）
〔５〕
さらに、（Ｇ）成分として、下記一般式（３）：

（式中、Ｒ⁵は独立に炭素原子数１〜８の脂肪族不飽和結合を含まない１価炭化水素基、ｄは５〜２，０００の整数である。）
で表される２３℃における動粘度が１０〜１００，０００ｍｍ²／ｓのオルガノポリシロキサンを含有することを特徴とする〔１〕〜〔４〕のいずれかに記載の熱伝導性シリコーン組成物。
〔６〕
粘度が８００Ｐａ・ｓ以下である〔１〕〜〔５〕のいずれかに記載の熱伝導性シリコーン組成物。
〔７〕
〔１〕〜〔６〕のいずれかに記載の熱伝導性シリコーン組成物を硬化させてなる熱伝導性シリコーン硬化物。
〔８〕
熱伝導率が１．５Ｗ／ｍ・Ｋ以上である〔７〕記載の熱伝導性シリコーン硬化物。
〔９〕
硬度がアスカーＣ硬度計で４０以下である〔７〕又は〔８〕記載の熱伝導性シリコーン硬化物。
〔１０〕
発熱性電子部品と熱放散部材との間に介装され、発熱性電子部品からの熱を熱放散部材に伝熱し、放熱するための伝熱部材用である〔７〕〜〔９〕のいずれかに記載のシリコーン硬化物。 Therefore, this invention provides the following heat conductive silicone composition and its hardened | cured material.
[1]
(A) Organopolysiloxane having at least two alkenyl groups in one molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: The number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to the number of moles of alkenyl groups derived from component (A). 5.0 times the amount,
(C) Thermally conductive filler in which 50% by mass or more of the total mass of the thermally conductive filler is occupied by magnesium oxide pretreated with the hydrophobic treating agent (E): 200 to 1,600 parts by mass,
(D) Platinum group metal-based curing catalyst: 0.1 to 1,000 ppm in terms of platinum group metal element mass relative to component (A),
A hydrophobized magnesium oxide,
(C-1) a hydrophobically treated powder of magnesium oxide having an average particle size of 0.1 μm or more and less than 40 μm and (C-2) a hydrophobically treated powder of magnesium oxide having an average particle size of 40 μm or more and less than 80 μm, (C-1) and The content ratio of (C-2) component is (C-1) / (C-2) = 1-3 / 2-4 by mass ratio, The heat conductive silicone composition characterized by the above-mentioned.
[2]
Hydrophobic-treated magnesium oxide was previously hydrophobized at a ratio of 0.05 to 3.0% by mass with respect to the total mass of magnesium oxide by the hydrophobic treating agent (E), and the hydrophobic treating agent (E)
(E-1) The following general formula (1):
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
And / or (E-2) the following general formula (2):

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
The thermally conductive silicone composition according to [1], wherein the molecular chain fragment end represented by the formula is dimethylpolysiloxane blocked with a trialkoxysilyl group.
[3]
(C) The heat conductive silicone composition according to [1] or [2], further containing aluminum oxide as a heat conductive filler.
[4]
Further, as the component (F), 0.01 to 50 parts by mass of an alkoxysilane compound of the following general formula (1) and / or dimethylpolysiloxane of the general formula (2) is added to 100 parts by mass of the component (A). The heat conductive silicone composition according to any one of [1] to [3].
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
[5]
Further, as the component (G), the following general formula (3):

(In the formula, R ⁵ is independently a monovalent hydrocarbon group not containing an aliphatic unsaturated bond having 1 to 8 carbon atoms, and d is an integer of 5 to 2,000.)
The heat conductive silicone composition according to any one of [1] to [4], wherein the composition contains an organopolysiloxane having a kinematic viscosity at 23 ° C. of 10 to 100,000 mm ² / s.
[6]
The heat conductive silicone composition according to any one of [1] to [5], wherein the viscosity is 800 Pa · s or less.
[7]
A thermally conductive silicone cured product obtained by curing the thermally conductive silicone composition according to any one of [1] to [6].
[8]
The thermally conductive silicone cured product according to [7], wherein the thermal conductivity is 1.5 W / m · K or more.
[9]
The heat-conductive silicone cured product according to [7] or [8], having a hardness of 40 or less according to an Asker C hardness meter.
[10]
Any one of [7] to [9], which is interposed between the heat-generating electronic component and the heat-dissipating member, transfers heat from the heat-generating electronic component to the heat-dissipating member, and dissipates the heat. A cured silicone product according to any one of the above.

  According to the present invention, by using 50% by mass or more of the hydrothermally treated magnesium oxide having different particle diameters in a predetermined ratio in the total thermal conductive filler, the thermal conductivity can be obtained without wearing the reaction kettle during kneading. It is possible to provide a thermally conductive silicone composition that gives a silicone cured product excellent in moisture resistance at 1.5 W / m · K or more, and a cured product thereof.

Hereinafter, the present invention will be described in detail.
[(A) Alkenyl group-containing organopolysiloxane]
The alkenyl group-containing organopolysiloxane as component (A) is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, and serves as a main component of the composition of the present invention. Usually, the main chain part is generally composed of repeating diorganosiloxane units, but this may be a part of the molecular structure containing a branched structure or cyclic. However, linear diorganopolysiloxane is preferred from the viewpoint of physical properties such as mechanical strength of the cured product.

  The functional group other than the alkenyl group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group. , Pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, alkyl group such as dodecyl group, cycloalkyl group such as cyclopentyl group, cyclohexyl group, cycloheptyl group, phenyl group, tolyl group, Aryl group such as xylyl group, naphthyl group, biphenylyl group, benzyl group, phenylethyl group, phenylpropyl group, aralkyl group such as methylbenzyl group, and part of hydrogen atoms to which carbon atoms of these groups are bonded or All substituted by halogen atoms such as fluorine, chlorine and bromine, cyano groups, etc. , Chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6 , 6,6-nonafluorohexyl group and the like, typical ones having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl group An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group, cyanoethyl group, and phenyl group, chlorophenyl group , An unsubstituted or substituted phenyl group such as a fluorophenyl group. Moreover, it is not limited that all functional groups other than the alkenyl group bonded to the silicon atom are the same.

  Examples of the alkenyl group include those having usually 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, and cyclohexenyl group. A lower alkenyl group such as an allyl group is preferred, and a vinyl group is particularly preferred. In addition, although it is preferable that two or more alkenyl groups exist in the molecule, it is preferable that the alkenyl group is bonded only to the silicon atom at the end of the molecular chain in order to make the obtained cured product flexible.

Kinematic viscosity at 25 ° C. This organopolysiloxane is usually, 10~100,000mm ² / s, particularly preferably from 500~50,000mm ² / s. If the viscosity is too low, the storage stability of the resulting composition may deteriorate, and if it is too high, the extensibility of the obtained composition may deteriorate. The kinematic viscosity is a value when using an Ostwald viscometer.

  The organopolysiloxane of component (A) may be used alone or in combination of two or more having different viscosities.

[(B) Organohydrogenpolysiloxane]
The organohydrogenpolysiloxane of component (B) is an organohydrogenpolysiloxane having a hydrogen atom (Si-H group) directly bonded to 2 or more, preferably 2 to 100 silicon atoms on average in one molecule. It is a component that acts as a crosslinking agent for component (A). That is, the Si—H group in the component (B) and the alkenyl group in the component (A) are added by a hydrosilylation reaction promoted by the platinum group metal catalyst of the component (D) described later to form a crosslinked structure. A three-dimensional network structure is provided. In addition, when the number of Si-H groups is less than one, it does not harden.

（式中、Ｒ⁶は独立に脂肪族不飽和結合を含有しない非置換もしくは置換の１価炭化水素基又は水素原子であるが、少なくとも２個、好ましくは２〜１０個は水素原子であり、ｅは１以上の整数、好ましくは１０〜１００の整数である。） As the organohydrogenpolysiloxane, one represented by the following average structural formula (4) is used, but is not limited thereto.

(Wherein R ⁶ independently represents an unsubstituted or substituted monovalent hydrocarbon group or a hydrogen atom that does not contain an aliphatic unsaturated bond, but at least 2, preferably 2 to 10 are hydrogen atoms, e is an integer of 1 or more, preferably an integer of 10 to 100.)

In the formula (4), as the unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond other than the hydrogen atom of R ⁶ , for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, Cycloalkyl groups such as isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, etc., cyclopentyl group, cyclohexyl group, cycloheptyl group, etc. An aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, and the carbon atoms of these groups Some or all of the hydrogen atoms are substituted with halogen atoms such as fluorine, chlorine, bromine, cyano groups, etc. Groups such as chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, fluorophenyl, cyanoethyl, 3,3,4,4,5 5,6,6,6-nonafluorohexyl group and the like, typical examples having 1 to 10 carbon atoms, especially typical ones having 1 to 6 carbon atoms, preferably An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group, a cyanoethyl group, and a phenyl group; An unsubstituted or substituted phenyl group such as a chlorophenyl group and a fluorophenyl group. Further, R ⁶ is not limited to being all the same.

  Component (B) is added in an amount such that the Si-H group derived from component (B) is 0.1 to 5.0 moles per mole of alkenyl group derived from component (A), preferably 0.3. -2.0 mol, more preferably 0.5-1.5 mol. When the amount of the Si-H group derived from the component (B) is less than 0.1 mol relative to 1 mol of the alkenyl group derived from the component (A), the cured product does not have sufficient strength or as a molded product. The shape cannot be maintained and cannot be handled. On the other hand, if it exceeds 5.0 mol, the cured product becomes inflexible and the cured product becomes brittle.

[(C) Thermally conductive filler]
The thermally conductive filler as component (C) contains 50% by mass or more of magnesium oxide whose surface according to a predetermined blending composition has been subjected to a hydrophobic treatment. When other fillers are contained, the surface is not necessarily subjected to a hydrophobic treatment. Aluminum oxide is preferably not used. (C) The total compounding quantity of a component needs to be 200-1,600 mass parts with respect to 100 mass parts of (A) component, Preferably it is 400-1,200 mass parts. When the blending amount is less than 200 parts by mass, the resulting composition has poor thermal conductivity and poor storage stability. When it exceeds 1,600 parts by mass, the composition has excellent extensibility. The molded product is poor and has low strength.

  (C) Hydrophobic-treated magnesium oxide is required to be contained in an amount of 50% by mass or more, preferably 70% by mass or more based on the total mass of the component (C). The upper limit is not particularly limited and may be 100% by mass. Magnesium oxide is used in combination with an average particle size of 0.1 μm or more and less than 40 μm and an average particle size of 40 μm or more and less than 80 μm, and preferably an average particle size of 10-30 μm and an average particle size of 50- 70 μm combination. The hydrophobically treated magnesium oxide includes (C-1) a hydrophobic treated powder of magnesium oxide having an average particle size of 0.1 μm or more and less than 40 μm, and (C-2) a hydrophobic treated powder of magnesium oxide having an average particle size of 40 μm or more and less than 80 μm. The blending ratio is (C-1) / (C-2) = 1-3 / 2-4 by mass ratio, preferably (C-1) / (C-2) = 1. 5-2.5 / 2.5-3.5.

The aluminum oxide used in the present invention may or may not have a hydrophobic surface. The average particle diameter of the non-hydrophobic treated aluminum oxide is preferably 5 to 300 μm, particularly preferably 5 to 200 μm, and is preferably used in an amount of less than 50% by mass based on the total weight of the component (C).
In the present invention, the average particle diameter is a volume-based cumulative average particle diameter (median diameter) measured by Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd.

  When the blending amount of magnesium oxide is less than 50% by mass, the specific gravity of the composition increases due to an increase in the ratio of aluminum oxide (alumina), and wear of the reaction kettle and stirring blade tends to occur. On the other hand, when the ratio of the particle size of magnesium oxide is outside the above range, the viscosity of the composition is remarkably increased, and molding of a cured product becomes very difficult. These heat conductive fillers can usually use commercially available ones.

  Here, the hydrophobic treatment method will be described. It is particularly preferable to use the following components (E-1) and / or (E-2) as the hydrophobic treatment agent (E). In the present invention, magnesium oxide, which is the component (C) that has been previously hydrophobically treated with a hydrophobic treating agent, can be used to more efficiently disperse magnesium oxide in the matrix composed of the component (A). Also, the surface of the aluminum oxide can be subjected to a hydrophobic treatment using the component (E).

(E-1) Component:
The component (E-1) is represented by the following general formula (1)
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
It is the alkoxysilane compound represented by these.

In the general formula (1), examples of the alkyl group represented by R ¹ include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. When the number of carbon atoms of the alkyl group represented by R ¹ satisfies the range of 6 to 15, the wettability of the component (C) is sufficiently improved, the handleability is good, and the low temperature characteristics of the composition are good. .

Examples of the unsubstituted or substituted monovalent hydrocarbon group represented by R ² include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, Hexyl, heptyl, octyl, nonyl, decyl, dodecyl and other alkyl groups, cyclopentyl, cyclohexyl, cycloheptyl and other cycloalkyl groups, phenyl, tolyl, xylyl, naphthyl, biphenylyl Aryl groups such as benzyl groups, aralkyl groups such as benzyl groups, phenylethyl groups, phenylpropyl groups, and methylbenzyl groups, and some or all of the hydrogen atoms to which the carbon atoms of these groups are bonded are fluorine, chlorine, Groups substituted with halogen atoms such as bromine, cyano groups, etc., for example, chloromethyl group, 2-bromoethyl 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group Typical examples are those having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl, ethyl, propyl, chloromethyl An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as a group, a bromoethyl group, a 3,3,3-trifluoropropyl group, a cyanoethyl group, and an unsubstituted or substituted phenyl group, a chlorophenyl group, a fluorophenyl group, etc. A substituted phenyl group may be mentioned. Examples of R ³ include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group.

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００、好ましくは５〜７０、特に好ましくは１０〜５０の整数である。）
で表される分子鎖片末端がトリアルコキシシリル基で封鎖されたジメチルポリシロキサンである。 (E-2) Component:
The component (E-2) is represented by the following general formula (2)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100, preferably 5 to 70, and particularly preferably 10 to 50.)
Is a dimethylpolysiloxane in which one end of a molecular chain represented by is blocked with a trialkoxysilyl group.

In the general formula (2), the alkyl group represented by R ⁴ is exemplified by the same type as the alkyl group represented by R ³ in the general formula (1).

  As the hydrophobic treatment agent for the component (E), either the component (E-1) or the component (E-2) may be combined. When using together (E-1) component and (E-2) component, it is preferable to use it by the ratio of (E-1) / (E-2) = 2-4 / 1-3 by mass ratio. The hydrophobization treatment of magnesium oxide as component (C) is performed by stirring magnesium oxide and a predetermined amount of hydrophobic treatment agent in a mixer at about 100 to 120 ° C. and then drying at about 100 to 150 ° C. . However, the processing method is not limited to this method.

  The treatment amount in the hydrophobic treatment is preferably 0.05 to 3.0% by mass, more preferably 0.2 to 2.0% by mass, based on the total mass of magnesium oxide. When the treatment amount is less than 0.05% by mass, the magnesium oxide may not be sufficiently hydrophobically treated and may not be uniformly dispersed in the matrix composed of the component (A). On the other hand, when the treatment amount exceeds 3.0% by mass, condensation occurs between trimethoxysilyl groups in the component (E), and the effect as a treatment agent may be reduced.

[(D) Curing catalyst]
The (D) component white metal-based curing catalyst is a catalyst for accelerating the addition reaction of the (A) component-derived alkenyl group and the (B) component-derived Si-H group, and is used for the hydrosilylation reaction. Well-known catalysts are mentioned as the catalyst to be used. Specific examples thereof include platinum group metals such as platinum (including platinum black), rhodium and palladium, H ₂ PtCl ₄ · nH ₂ O, H ₂ PtCl ₆ · nH ₂ O, NaHPtCl ₆ · nH ₂ O. , KaHPtCl ₆ · nH ₂ O, Na ₂ PtCl ₆ · nH ₂ O, K ₂ PtCl ₄ · nH ₂ O, PtCl ₄ · nH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ · nH ₂ O (where, n is an integer of 0-6, preferably 0 or 6), such as platinum chloride, chloroplatinic acid and chloroplatinate, alcohol-modified chloroplatinic acid (see US Pat. No. 3,220,972) ), A complex of chloroplatinic acid and olefin (see US Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black, Platinum group metals such as palladium On a carrier such as alumina, silica, carbon, rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst), platinum chloride, chloroplatinic acid or chloroplatinate and vinyl group-containing siloxane, In particular, a complex with a vinyl group-containing cyclic siloxane may be mentioned.

  The amount of component (D) used may be a so-called catalytic amount, and is usually about 0.1 to 1,000 ppm in terms of mass of the platinum group metal element relative to component (A).

  The composition of the present invention can further contain the following components (F) to (H) as necessary.

[(F) Surface treatment agent]
A surface treating agent can be mix | blended in order to disperse | distribute the heat conductive filler which is (C) component uniformly in the matrix which consists of (A) component in the case of composition preparation.
In this case, examples of the surface treatment agent include an alkoxysilane compound represented by the above formula (1) and a dimethylpolysiloxane in which a molecular chain fragment end represented by the above formula (2) is blocked with a trialkoxysilyl group. . That is, although the same thing as the said hydrophobic processing agent can be used, you may use the same thing as what was used for the hydrophobic treatment of a heat conductive filler, or a different thing from this.
When the alkoxysilane compound of the above formula (1) and / or the dimethylpolysiloxane of the formula (2) is used as a surface treatment agent, the blending amount is 0.01 to 50 parts by mass with respect to 100 parts by mass of the component (A). In particular, the content is preferably 0.1 to 30 parts by mass. Increasing the proportion of this component can induce oil separation. When the ratio is small, the wettability between the polyorganosiloxane and the heat conductive filler is lowered, and a composition cannot be formed.

（式中、Ｒ⁵は独立に炭素原子数１〜１８の脂肪族不飽和結合を含まない１価炭化水素基、ｄは５〜２，０００の整数である。）
で表される２３℃における動粘度が１０〜１００，０００ｍｍ²／ｓのオルガノポリシロキサンを添加することができる。（Ｇ）成分は、１種単独で用いても、２種以上を併用してもよい。 [(G) Organopolysiloxane]
The thermal conductive silicone composition of the present invention has the following general formula (3) as the component (G) for the purpose of imparting properties such as viscosity adjustment of the thermal conductive silicone composition.

(In the formula, R ⁵ is independently a monovalent hydrocarbon group not containing an aliphatic unsaturated bond having 1 to 18 carbon atoms, and d is an integer of 5 to 2,000.)
It is possible to add an organopolysiloxane having a kinematic viscosity at 23 ° C. of 10 to 100,000 mm ² / s. (G) A component may be used individually by 1 type, or may use 2 or more types together.

R ⁵ is independently a monovalent hydrocarbon group that does not contain an unsubstituted or substituted aliphatic unsaturated bond having 1 to 18 carbon atoms. Examples of R ⁵ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group. Alkyl groups such as dodecyl group, cycloalkyl groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and biphenylyl group, benzyl group, phenylethyl group, phenylpropylene Groups in which some or all of the hydrogen atoms to which the carbon atoms of these groups are bonded are substituted with halogen atoms such as fluorine, chlorine and bromine, cyano groups, etc. For example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-to Fluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, etc. are mentioned. 1 to 10, particularly typical ones having 1 to 6 carbon atoms, preferably methyl group, ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl Group, an unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as a cyanoethyl group, and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, and a fluorophenyl group. Groups are preferred.

  From the viewpoint of the required viscosity, d is preferably an integer of 5 to 2,000, and particularly preferably an integer of 10 to 1,000.

Moreover, kinematic viscosity at 25 ° C. of component (G) is preferably 10~100,000mm ² / s, it is preferable in particular 100~10,000mm ² / s. When the kinematic viscosity is lower than 10 mm ² / s, the cured product of the resulting composition tends to generate oil bleeding. When the kinematic viscosity is larger than 100,000 mm ² / s, the flexibility of the obtained heat conductive composition tends to be poor.

  When component (G) is added to the composition of the present invention, the amount added is not limited and may be any amount that can provide the desired effect, but is preferably 100 parts by weight of component (A). It is 0.1-100 mass parts, More preferably, it is 1-50 mass parts. When the addition amount is within this range, it is easy to maintain good fluidity and workability of the heat conductive composition before curing, and it is easy to fill the composition with the heat conductive filler of component (C). It is.

[(H) Reaction control agent]
As the addition reaction control agent as the component (H), all known addition reaction control agents used in ordinary addition reaction curable silicone compositions can be used. Examples thereof include acetylene compounds such as 1-ethynyl-1-hexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. The amount used is an effective amount, and is preferably about 0.01 to 1 part by weight, particularly about 0.1 to 0.8 part by weight with respect to 100 parts by weight of component (A). If the amount is too large, the curing reaction may not proceed and the molding efficiency may be impaired.

[Other ingredients]
The heat conductive silicone composition of the present invention may further contain other components as long as the objects and effects of the present invention are not impaired. For example, optional components such as a heat resistance improver such as iron oxide and cerium oxide; a viscosity modifier such as silica; a colorant; and a release agent can be blended.

[Viscosity of composition]
The viscosity of the thermally conductive silicone composition of the present invention is preferably 800 Pa · s or less, more preferably 400 Pa · s or less, further preferably 200 Pa · s or less, and particularly preferably 100 Pa · s or less at 25 ° C. If the viscosity is too high, moldability may be impaired. In the present invention, this viscosity is based on measurement with a B-type viscometer.

[Method for Preparing Thermally Conductive Silicone Composition]
The heat conductive silicone composition of this invention can be prepared by mixing each component mentioned above uniformly according to a conventional method.

[Method of curing thermally conductive silicone cured product]
The curing conditions for molding the thermally conductive silicone composition may be the same as those of a known addition reaction curable silicone rubber composition. For example, it is sufficiently cured at room temperature, but may be heated as necessary. Preferably, the addition curing is performed at 100 to 120 ° C. for 8 to 12 minutes. Such a molded product of the present invention is excellent in thermal conductivity.

[Thermal conductivity of molded body]
As for the thermal conductivity of the molded body (heat conductive silicone cured product) in the present invention, the measured value at 25 ° C. measured by the hot disk method is preferably 1.5 W / m · K or more. When the thermal conductivity is less than 1.5 W / m · K, application to a heating element having a large calorific value becomes impossible.

[Hardness of molded body]
The hardness of the molded product in the present invention is 40 or less, preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less as measured at 25 ° C. measured with an Asker C hardness meter. When the hardness exceeds 40, it may be difficult to exhibit good heat dissipation characteristics without applying stress to the heat radiating body due to deformation along the shape of the heat radiating body.

[Use of molded body]
The molded body is interposed between a heat boundary surface of a heat generating electronic component and a heat dissipating member such as a heat sink or a circuit board, for example, between a heat generating component and a heat dissipating component in an electronic device. It can be used as a heat transfer member for transferring the heat from the heat to the heat dissipation member and dissipating it.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

（式中、Ｘはビニル基であり、ｆは下記粘度を与える数である。）
（Ａ−１）動粘度：６００ｍｍ²／ｓ
（Ａ−２）動粘度：３０，０００ｍｍ²／ｓ The components (A) to (H) used in the following examples and comparative examples are shown below.
(A) component:
Organopolysiloxane represented by the following formula (5).

(In the formula, X is a vinyl group, and f is a number giving the following viscosity.)
(A-1) Kinematic viscosity: 600 mm ² / s
(A-2) Kinematic viscosity: 30,000 mm ² / s

（式中、ｇは２８、ｈは２である。） (B) component:
Organohydrogenpolysiloxane represented by the following formula (6).

(In the formula, g is 28 and h is 2.)

(C) component:
Magnesium oxide having an average particle size as follows.
(C-1): 1.0 mass% of the following (E-1) component added to the mass of magnesium oxide having an average particle diameter of 10 μm was reacted and dried at 110 to 120 ° C. in a Henschel mixer. Hydrophobic treated powder (C-2): 0.5 mass% of the following (E-1) component added to the mass of magnesium oxide having an average particle diameter of 50 μm in a Henschel mixer Hydrophobic treated powder (C-3) which was reacted and dried at 120 ° C .: 1.0 mass% of the following (E-2) component added to the mass of magnesium oxide having an average particle diameter of 10 μm Hydrophobic-treated powder (C-4) which was reacted and dried at 110 to 120 ° C. in a Henschel mixer: 0.5 mass% of the following (E-2) based on the mass of magnesium oxide having an average particle diameter of 50 μm Henschel with added ingredients Hydrophobic-treated powder (C-5) which was reacted and dried at 110 to 120 ° C. in a Xerer: magnesium oxide (C-6) having an average particle size of 10 μm: magnesium oxide (C-7) having an average particle size of 50 μm: average Aluminum oxide (C-8) having a particle size of 10 μm: Aluminum oxide having an average particle size of 45 μm

(D) component:
5% by mass chloroplatinic acid 2-ethylhexanol solution

(E-1) Component:
Trimethoxysilane represented by the following formula (7).

(E-2) component, (F) component:
A dimethylpolysiloxane in which one end having an average degree of polymerization of 30 represented by the following formula (8) is blocked with a trimethoxysilyl group.

（式中、ｊは１００である。） (G) component:
Dimethylpolysiloxane represented by the following formula (9) as a plasticizer.

(Where j is 100)

(H) component:
Ethynylmethylidenecarbinol as an addition reaction control agent.

[Examples 1-8, Comparative Examples 1-8]
In Examples 1 to 8 and Comparative Examples 1 to 8, compositions (A) to (H) were prepared as described below using predetermined amounts shown in the following table, molded and cured, and according to the following method. The moldability of the composition was confirmed and the wear of the reaction kettle was confirmed. Moreover, according to the following method with respect to the obtained hardened | cured material, the measurement of the heat conductivity, the high temperature, high humidity test, and the measurement of hardness were implemented. The results are also shown in the table.

[Preparation of composition]
Components (A), (C), (F), and (G) were added in predetermined amounts shown in Examples 1 to 8 and Comparative Examples 1 to 8 in the following table, and kneaded for 60 minutes with a planetary mixer.
Therein, (D) and (H) components are added in predetermined amounts in Examples 1 to 8 and Comparative Examples 1 to 8 shown in the table below, and Shin-Etsu Chemical Co., Ltd. is used as an internal addition release agent that promotes release from the separator. An effective amount of KF-54, which is a phenyl-modified silicone oil manufactured by Co., Ltd., was added and further kneaded for 60 minutes.
The component (B) was further added in predetermined amounts shown in Examples 1 to 8 and Comparative Examples 1 to 8 in the following table, and kneaded for 30 minutes to obtain a composition.

[Molding method]
The obtained composition was poured into a 60 mm × 60 mm × 6 mm mold and molded at 120 ° C. for 10 minutes using a press molding machine.

[Evaluation method]
(A) Thermal conductivity:
The compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 8 were cured into a sheet having a thickness of 6 mm, and two sheets were used to obtain a thermal conductivity meter (TPA-501, Kyoto Electronics Industry Co., Ltd.). The thermal conductivity of the sheet was measured using a product name.
(B) Hardness:
The compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 8 were cured into a sheet having a thickness of 6 mm, and the two sheets were stacked and measured with an Asker C hardness meter.
(C) Moisture resistance:
The cured products obtained in Examples 1 to 8 and Comparative Examples 1 to 8 were subjected to a high temperature and high humidity test under the conditions of 85 ° C./85% Rh, and the hardness after 200 hours was measured using an Asker C hardness meter. It was measured. The initial hardness was set to 20. When the hardness after 200 hours increased to 22 or more, it was described as “None”, and when the hardness was 21 or less, “Present”.

(D) Formability:
When molding the obtained heat conductive silicone composition, it is “good” when the operation can be completed without any problem with respect to the operation to be poured into the mold. When it was possible, it was set as “impossible”.
(E) Reaction kettle wear:
In the stage of adjusting the composition according to the above adjustment method, the reaction kettle was shaved and “Yes” was indicated if the black component was visually confirmed, and “No” if not confirmed. Since the composition when alumina and magnesium hydroxide are used for the thermally conductive filler is white, the black component is clearly and easily mixed.

  In the magnesium oxide (magnesia) that has been hydrophobically treated as in Comparative Example 1, when the particle system ratio of 10 μm and 50 μm is outside the range of 1 to 3/2 to 4, the viscosity of the composition is remarkably increased, and molding is difficult. It was difficult. When the content of hydrophobically treated magnesium oxide is less than 50% by mass with respect to the total mass of the thermally conductive filler as in Comparative Example 2, mixing of the black substance was confirmed from the wear of the kettle due to aluminum oxide (alumina). It was done. In addition, as in Comparative Examples 3 and 4, when a cured product was molded using magnesium oxide that was not subjected to hydrophobic treatment, the hardness increased greatly under high temperature and high humidity, and sufficient moisture resistance was not exhibited. In addition, as in Comparative Examples 5 to 8, the magnesium oxide treated with the component (E-1) or (E-2) is less than 50% by mass, and when untreated magnesium oxide is used in combination, The moisture resistance of the molded product was insufficient.

  On the other hand, as in Examples 1 to 8, magnesium oxide having a particle size of 50 μm and 10 μm treated with the component (E-1) or (E-2) as a hydrophobic treatment agent is used as the total mass of the thermally conductive filler. When the composition is configured with a content ratio of 10 μm / 50 μm = 1 to 3/2 to 4 using 50% by mass or more in total, the reaction kettle is not worn out and is stably cured. It was possible to mold things. Further, the cured product had a thermal conductivity of 1.5 W / m · K or more, and was excellent in moisture resistance under high temperature and high humidity.

Claims (10)

(A) Organopolysiloxane having at least two alkenyl groups in one molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: The number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to the number of moles of alkenyl groups derived from component (A). 5.0 times the amount,
(C) Thermally conductive filler in which 50% by mass or more of the total mass of the thermally conductive filler is occupied by magnesium oxide pretreated with the hydrophobic treating agent (E): 200 to 1,600 parts by mass,
(D) Platinum group metal-based curing catalyst: 0.1 to 1,000 ppm in terms of platinum group metal element mass relative to component (A),
A hydrophobized magnesium oxide,
(C-1) a hydrophobically treated powder of magnesium oxide having an average particle size of 0.1 μm or more and less than 40 μm and (C-2) a hydrophobically treated powder of magnesium oxide having an average particle size of 40 μm or more and less than 80 μm, (C-1) and The content ratio of (C-2) component is (C-1) / (C-2) = 1-3 / 2-4 by mass ratio, The heat conductive silicone composition characterized by the above-mentioned. Hydrophobic-treated magnesium oxide was previously hydrophobized at a ratio of 0.05 to 3.0% by mass with respect to the total mass of magnesium oxide by the hydrophobic treating agent (E), and the hydrophobic treating agent (E)
(E-1) The following general formula (1):
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
And / or (E-2) the following general formula (2):

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
2. The thermally conductive silicone composition according to claim 1, which is a dimethylpolysiloxane in which one end of a molecular chain represented by the formula is blocked with a trialkoxysilyl group.   (C) The heat conductive silicone composition of Claim 1 or 2 which contains an aluminum oxide further as a heat conductive filler. Further, as the component (F), 0.01 to 50 parts by mass of an alkoxysilane compound of the following general formula (1) and / or dimethylpolysiloxane of the general formula (2) is added to 100 parts by mass of the component (A). The thermally conductive silicone composition according to any one of claims 1 to 3.
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.) Further, as the component (G), the following general formula (3):

(In the formula, R ⁵ is independently a monovalent hydrocarbon group not containing an aliphatic unsaturated bond having 1 to 8 carbon atoms, and d is an integer of 5 to 2,000.)
The thermally conductive silicone composition of any one of claims 1 to 4, kinematic viscosity, characterized in that it contains an organopolysiloxane 10~100,000mm ² / s at in 23 ° C. expressed.   The heat conductive silicone composition according to any one of claims 1 to 5, wherein the viscosity is 800 Pa · s or less.   The heat conductive silicone hardened | cured material formed by hardening | curing the heat conductive silicone composition of any one of Claims 1-6.   The thermally conductive silicone cured product according to claim 7, wherein the thermal conductivity is 1.5 W / m · K or more.   The thermally conductive silicone cured product according to claim 7 or 8, having a hardness of 40 or less as measured by an Asker C hardness meter.   The heat transfer member is interposed between the heat-generating electronic component and the heat dissipation member, and is used for a heat transfer member for transferring heat from the heat-generating electronic component to the heat dissipation member and dissipating the heat. The cured silicone product according to Item.